Electrolyte composition and battery

Abstract

The present disclosure provides an electrolyte composition comprising: a polymer that is capable of preferentially conducting alkali metal ions; and an ionic compound, wherein the ionic compound includes an anion having a donor number of 37 or less as measured for a 1-ethyl-3-methylimidazolium salt.

Description

Electrolyte composition and battery

[0001] The present disclosure relates to electrolyte compositions and batteries.

[0002] Batteries such as lithium ion batteries, which charge and discharge through the movement of metal ions between a positive electrode and a negative electrode, have been the subject of vigorous research due to their high capacity. Known electrolytes for lithium ion batteries and the like include solutions of lithium salts containing organic solvents or ionic liquids. However, from the perspectives of safety and processability, research into solid electrolytes, polymer electrolytes, and the like is also underway (see Patent Documents 1 and 2). In addition to lithium ion batteries, research is also underway into batteries using other alkali ions, such as sodium and potassium, which are more abundant than lithium.

[0003] International Publication No. 2007 / 125845 Japanese Patent Application Laid-Open No. 2021-88695

[0004] Polymer electrolytes generally adhere more easily to electrodes than solid electrolytes, and therefore tend to have lower contact resistance with the electrodes. However, the inventors have conducted extensive research and found that polymer electrolytes containing polymers having functional groups that serve as counter anions for alkali metal ions have high resistance depending on the functional groups, leaving room for improvement. Furthermore, it would be useful if this improvement could reduce the resistance between the electrodes and the electrolyte.

[0005] The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide an electrolyte composition that allows a sufficiently large current to flow at a low voltage, and a battery including the electrolyte composition.

[0006] The present disclosure includes the following embodiments. [1] An electrolyte composition comprising: a polymer capable of preferentially conducting alkali metal ions; and an ionic compound, wherein the ionic compound contains an anion having a donor number of 37 or less as measured with a 1-ethyl-3-methylimidazolium salt. [2] The electrolyte composition of [1], wherein the transference number of the alkali metal ion is 0.5 or more. [3] The electrolyte composition of [1] or [2], wherein the polymer capable of preferentially conducting alkali metal ions contains a lithium ion or a sodium ion. [4] The electrolyte composition of any one of [1] to [3], wherein the ionic compound is a compound such that, when A is the Raman shift attributable to the anion constituting the ionic compound in a Raman spectrum obtained by Raman spectroscopy of the ionic compound, and B is the Raman shift attributable to the anion constituting the ionic compound in a Raman spectrum obtained by Raman spectroscopy of the electrolyte composition, B≦A. [5] The electrolyte composition of any one of [1] to [4], further comprising a nonionic organic solvent. [6] The electrolyte composition according to [5], wherein the nonionic organic solvent further comprises one or more organic solvents selected from the group consisting of carbonate-based solvents, ether-based solvents, fluorine-based solvents, nitrile-based solvents, lactone-based solvents, phosphate ester-based solvents, and sulfone-based solvents. [7] The electrolyte composition according to [5] or [6], wherein the nonionic organic solvent has a relative dielectric constant of 21 or more. [8] The electrolyte composition according to any one of [1] to [7], wherein the functional group having an anion comprises one or more groups selected from the group consisting of an alkali metal substituted sulfonylimide group, an alkali metal substituted sulfonic acid group, and an alkali metal substituted carboxylic acid group. [9] The electrolyte composition according to any one of [1] to [8], wherein the polymer capable of preferentially conducting alkali metal ions does not hydrolyze in air.

[10] A battery comprising the electrolyte composition according to any one of [1] to [9].

[0007] According to the present disclosure, it is possible to provide an electrolyte composition that allows a sufficient amount of current to flow at a low voltage, and a battery including the electrolyte composition.

[0008] Fig. 1 is a graph showing the results of measuring the maximum DC current density using the electrolyte composition of Example 15. Fig. 2 is a graph showing the results of measuring the maximum DC current density using the electrolyte composition of Comparative Example 3.

[0009] An electrolyte composition according to one embodiment of the present disclosure includes a polymer capable of preferentially conducting alkali metal ions and an ionic compound, and the ionic compound includes an anion having a donor number of 37 or less as measured for a 1-ethyl-3-methylimidazolium salt. As described above, the electrolyte composition according to this embodiment has low resistance, which facilitates the movement of Li cations at the interface between the electrode and the electrolyte, enabling operation at a voltage that is sufficiently practical. Furthermore, the electrolyte composition according to this embodiment also tends to improve the selective transport of lithium ions.

[0010] The electrolyte composition includes an ionic compound containing an anion having a donor number of 37 or less, as measured with a 1-ethyl-3-methylimidazolium salt. Such an ionic compound interacts with the anionic functional group of the polymer. The interaction of the cationic portion of the ionic compound with the anionic functional group can relax the anionic nature of the polymer. Furthermore, alkali metal ions are also attracted to the anionic portion of the ionic compound, thereby relativizing and weakening the constraint from the anionic functional group of the polymer, thereby improving the conductivity of alkali metal ions in the electrolyte. This action can reduce the resistance of the electrolyte composition. The electrolyte composition of this embodiment improves resistance between the electrode and the electrolyte interface.

[0011] In any case herein, examples of the "substituent" include both organic groups and groups other than organic groups (inorganic groups). In this specification, the term "organic group" refers to a group having a chemical structure in which at least one hydrogen atom has been removed from an organic compound. When referring to the "organic group" in any case herein, regardless of the valence of the organic group, examples include hydrocarbon groups or groups in which some carbon atoms of a hydrocarbon group have been replaced with heteroatoms, and groups in which at least one hydrogen atom of a hydrocarbon group or a group in which some carbon atoms of a hydrocarbon group have been replaced with heteroatoms has been substituted with a substituent. When the organic group has a ring structure, the ring may be either a heterocycle or a carbocycle, and may be either a monocycle or a fused ring. In any case herein, examples of the hydrocarbon group include both aliphatic hydrocarbon groups and aromatic hydrocarbon groups. In any case herein, examples of the aliphatic hydrocarbon group include linear hydrocarbon groups, branched hydrocarbon groups, and cyclic hydrocarbon groups. Furthermore, in any case herein, examples of the hydrocarbon group include both saturated hydrocarbon groups and unsaturated hydrocarbon groups. In this specification, an aromatic hydrocarbon group refers to a hydrocarbon group having an aromatic moiety such as a benzene ring, and may also have an aliphatic moiety. Furthermore, in this specification, a cyclic hydrocarbon group refers to a hydrocarbon group having an aliphatic carbon ring moiety, and may also have a linear or branched aliphatic moiety. The heteroatom substituting the carbon atom is not particularly limited, and examples thereof include a boron atom, an oxygen atom, a nitrogen atom, a silicon atom, a phosphorus atom, and a sulfur atom. Specifically, the organic group may contain a linking group containing a heteroatom, such as an -O- (ether bond), an -S- (thioether bond), a sulfonyl group, a sulfinyl group, a secondary amino group, or a tertiary amino group. In any case in this specification, specific examples of the organic group include a substituted or unsubstituted hydrocarbon group, and a linking group in which one or more carbon atoms (methylene groups) in the hydrocarbon group contain a heteroatom such as —O— (ether bond), —S— (thioether bond), —C(═O)—, —C(═O)O—, or —C(═O)NR— (R is a monovalent organic group) (the linking group may be a divalent linking group).In any case herein, examples of the inorganic group include an electron-withdrawing group and an electron-donating group, and specific examples thereof include a halogen atom and —NH. ２ , -NH ３ ＋ , —CN, sulfonic acid group and its salts or esters, —NO ２ etc.

[0012] <Polymer Capable of Preferentially Conducting Alkali Metal Ions> A polymer capable of preferentially conducting alkali metal ions (hereinafter also simply referred to as a polymer) may be any polymer that satisfies at least one of the following conditions (A) and (B). The polymer may simply be referred to as a polymer capable of conducting alkali metal ions. (A) When the transference number of alkali metal ions is measured at room temperature (25°C) for a composition containing 33 mass% of a polymer and 67 mass% of a nonionic plasticizer, the transference number is 0.4 or greater. (B) When the transference number of alkali metal ions is measured at room temperature (25°C) for a composition containing 31.9 mass% of a polymer, an alkali metal salt, and the remainder of a nonionic plasticizer, and having an alkali metal ion concentration of 0.3 mol / L, the transference number is 0.4 or greater.

[0013] In (A) and (B), the transport number of the alkali metal ion may be 0.5 or more, 0.6 or more, or 0.7 or more. The transport number of the alkali metal ion may be, for example, 0.9 or less.

[0014] The alkali metal ions contained in the composition may be countercations for the anionic functional groups of the polymer.

[0015] The non-ionic plasticizer may be at least one of an organic solvent and another resin such as a fluorine-based resin.

[0016] The organic solvent may be an aprotic solvent. The aprotic solvent may be at least one selected from the group consisting of carbonate-based solvents, fluorine-based solvents, and ether-based solvents. The organic solvent may be a mixed solvent of ethylene carbonate and propylene carbonate (volume ratio 1:1).

[0017] The fluororesin is preferably a resin having a carbon chain as the main chain. The carbon chain may be formed by radical polymerization of an ethylenically unsaturated group. The fluororesin may be PVDF-HFP.

[0018] The polymer has the anionic functional group. The polymer may contain a structural unit (hereinafter also referred to as structural unit (A)) having an alkali metal ion as a counter cation of the anionic functional group. The polymer may contain, in addition to the structural unit (A), a structural unit (hereinafter also referred to as structural unit (B)) having a functional group that functions as an anion receptor. The polymer may have one or more types of structural unit (A). The polymer may also have one or more types of structural unit (B).

[0019] The polymer may contain, as the alkali metalated group, one or more groups selected from the group consisting of an alkali metalated sulfonylimide group, an alkali metalated sulfonic acid group, an alkali metalated carboxylic acid group, and an alkali metalated phenolic hydroxyl group.

[0020] Here, in this specification, an alkali metalated group refers to a group in which an anionic functional group, which is a conjugate base of the acid form of the group, forms a salt with an alkali metal ion. Specific examples include an alkali metalated sulfonylimide group, an alkali metalated sulfonic acid group, an alkali metalated carboxylic acid group, and an alkali metalated phenolic hydroxyl group. An alkali metalated sulfonylimide group is a sulfonylimide acid group (-SO ２ -NH-SO ２ - group) in which H is substituted with an alkali metal element A ２ -NA-SO ２ - group ([-SO ２ -N-SO ２ -]－ A ＋ The alkali metal sulfonic acid group refers to a sulfonic acid group (—SO ３ H group) in which H is replaced by an alkali metal element A. ３ A group ([-SO ３ ] － A ＋ The alkali metal carboxylic acid group refers to a —COOA group ([—COO] group) in which H of a carboxylic acid group (—COOH group) is substituted with an alkali metal element A. － A ＋ The alkali metal phenolic hydroxyl group refers to an —OA group (—O group) in which the H of the —OH group, which is a phenolic hydroxyl group, is substituted with an alkali metal element A. － A ＋ This refers to the group.

[0021] The structure of the polymer is not particularly limited, but examples thereof include those having a carbon chain as the main chain, and the carbon chain may be formed by radical addition polymerization of a monomer having an ethylenically unsaturated group.

[0022] The alkali metal element A may contain at least one selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium, may contain at least one selected from the group consisting of lithium, sodium, and potassium, may contain at least one of lithium and sodium, or may contain lithium.

[0023] The content of one alkali metal element among the alkali metal elements contained in the polymer may be, for example, 80 mol% or more, 85 mol% or more, or 90 mol% or more. The content of one alkali metal element among the alkali metal elements contained in the polymer may be, for example, 100 mol%, or may be 98 mol% or less, or 95 mol% or less. The one alkali metal element may be potassium, sodium, or lithium, or may be sodium, lithium, or lithium.

[0024] The structural unit (A) may contain at least one of a structural unit represented by the following formula (A1) and a structural unit represented by the following formula (A2):１ ~R ３ and Y are omitted, and in formula (A2), R ４ , R ５ The structure excluding Z is also simply called an ethylene unit. (In formula (A1), Y is a monovalent group converted to an alkali metal. R １ ~R ３ are each independently a hydrogen atom or a monovalent substituent, or R １ and R ２ One of them is R ３ and form a ring together, and the other is a hydrogen atom or a monovalent substituent. １ ~R ３ may have the above-mentioned alkali metalated group. (In formula (A2), Z is a divalent group converted to an alkali metal. R ４ and R ５ are each independently a hydrogen atom or a monovalent substituent, or R ４ and R ５ are joined together to form a ring. ４ and R ５ may have the above-mentioned alkali metalated group.

[0025] In formula (A1), Y may contain one or more groups selected from the group consisting of an alkali metal substituted sulfonylimide group, an alkali metal substituted sulfonic acid group, an alkali metal substituted carboxylic acid group, and an alkali metal substituted phenolic hydroxyl group, or may contain one or more groups selected from the group consisting of an alkali metal substituted sulfonylimide group, an alkali metal substituted sulfonic acid group, and an alkali metal substituted carboxylic acid group. One or more functional groups may be used as Y.

[0026] In formula (A1), R １ ~R ３ The monovalent substituent as R may be a monovalent organic group. １ ~R ３ When R is a monovalent substituent, the substituent may be a monovalent organic group. The number of carbon atoms in the monovalent organic group may be, for example, 1 to 20, 1 to 15, 1 to 10, 1 to 5, or 1 to 3. １~R ３ At least one of may be a hydrogen atom, or all of may be hydrogen atoms.

[0027] In formula (A1), R １ and R ２ One of them is R ３ When R forms a ring together with １ or R ２ and R ３ In formula (A2), R forms a divalent substituent bonded to two carbon atoms of the ethylene unit of formula (A1). ４ and R ５ are taken together to form a ring, R ４ and R ５ form divalent substituents bonded to two carbon atoms of the ethylene unit of formula (A1), respectively. These rings may be either carbocyclic or heterocyclic. The number of ring members of these rings may be, for example, 4 to 10, 5 to 8, 5, or 6. A substituent may be bonded to the carbon atom or heteroatom that is a ring member.

[0028] In formula (A1), when Y contains an alkali metal-modified carboxylic acid group (-COOA group, A is an alkali metal), Y may be the -COOA group itself, or may be a monovalent organic group having a -COOA group. When Y is a monovalent organic group, the number of carbon atoms contained in the organic group may be, for example, 1 to 20, 1 to 15, 1 to 10, 1 to 5, or 1 to 3. The monovalent organic group may have one or more -COOA groups, or may have one -COOA group. In addition to the -COOA group, Y may have an electron-withdrawing group such as a halogen atom.

[0029] In formula (A1), Y is -R ９ -COOA, where R ９ is a divalent organic group or a covalent bond. The number of carbon atoms in the divalent organic group may be, for example, 1 to 19, 1 to 14, 1 to 9, 1 to 4, or 1 or 2.

[0030] In the formula (A1), when Y is a sulfonic acid group modified with an alkali metal, examples of Y include groups represented by the following formula (A3). (In formula (A3), R １９ is a covalent bond or a divalent organic group. A is an alkali metal element.

[0031] In formula (A3), the divalent organic group may have, for example, 1 to 20, 1 to 15, 1 to 10, 1 to 5, or 1 to 3 carbon atoms.

[0032] In formula (A3), the alkali metal substituted sulfonic acid group is —SO ３ A, -CH ２ -SO ３ A, -C ６ H ４ -SO ３ Examples include A.

[0033] The structural unit (A2) may be a group containing a maleimide ring having an alkali metal-modified group, and examples thereof include the following structural unit (A4). (In formula (A4), X is a divalent organic group having 1 to 20 carbon atoms, and Y １ is a halogen atom or a monovalent organic group having 1 to 20 carbon atoms, and A ＋ represents an alkali metal ion, and * represents the position where the structural unit (A4) is bonded to another structural unit.

[0034] In formula (A4), the number of carbon atoms owned by X may be, for example, 1 to 15, 2 to 10, or 3 to 8. The hydrocarbon group represented by X may be a phenylene group, an alkylene group having 1 to 8 carbon atoms, a polyoxyalkylene group, or a group in which some or all of the hydrogen atoms bonded to the carbon atoms of these groups have been substituted with halogen atoms such as fluorine atoms, or may be a phenylene group or a substituted phenylene group substituted with an alkyl group, a halogen atom, an electron-withdrawing group, or the like.

[0035] In formula (A4), Y １ is a monovalent organic group, Y １ The number of carbon atoms contained in Y may be, for example, 1 to 15, 1 to 10, 1 to 8, 1 to 5, or 1 to 3. １The hydrocarbon group as Y may be a phenyl group, an alkyl group having 1 to 5 carbon atoms, or a group in which some or all of the hydrogen atoms bonded to the carbon atoms of these groups have been substituted with halogen atoms such as fluorine atoms, or may be a fluorinated alkyl group having 1 to 5 carbon atoms, or a fluorinated alkyl group having 1 to 3 carbon atoms such as a trifluoromethyl group. The fluorinated alkyl group may be a perfluorinated alkyl group. １ When is a halogen atom, the halogen atom may be a fluorine atom or a chlorine atom, and may be a fluorine atom.

[0036] When the polymer contains the structural unit (B), the structural unit (B) functions as an anion receptor. An anion receptor is a chemical species that captures anions by forming electrostatic interactions, hydrogen bonds, acid-base complexes, or the like with anions. The structural unit (B) captures the counter anion of the alkali metal ion in the alkali metal salt and promotes dissociation between the counter anion and the alkali metal ion. This increases the mobility of the alkali metal ion. Meanwhile, since the counter anion is captured by the polymer via the structural unit (B), the mobility of the counter anion decreases. This is thought to result in an improvement in the transport number of the alkali metal ion. Furthermore, the increased mobility of the alkali metal ion also tends to improve the conductivity of the alkali metal ion. Low-molecular-weight chemical species (compounds, etc.) that function as anion receptors are known, and examples of such compounds include those described in U.S. Patent Nos. 6,022,643, 5,705,689, and 6,120,941.

[0037] The functional group functioning as an anion receptor may have Lewis acidity. In this case, the functional group can capture the anion by accepting the unshared electron pair of the anion and forming an acid-base complex. Examples of such functional groups include functional groups having an electron-deficient atom. Note that an electron-deficient atom refers to an atom that is covalently bonded to another atom but the electrons in the outermost shell of the atom do not form an octet. Examples of electron-deficient atoms include atoms belonging to Group 13 of the periodic table, and more specifically, may be at least one of aluminum and boron, or may be boron.

[0038] The functional group having a function as an anion receptor may be a group having an azaether moiety. The group having an azaether moiety is a group having an azaether compound as a substituent, and the azaether compound is formed by replacing —O— of an ether compound with —NR Ｅ - (where R Ｅ is a hydrogen atom or an organic group). The azaether moiety may be either a linear azaether moiety or a cyclic azaether moiety, or may have both a linear azaether moiety and a cyclic azaether moiety. The group having an azaether moiety may have an electron-withdrawing group, for example, in the hydrocarbon moiety.

[0039] The structural unit (B) may contain at least one structural unit represented by the following formula (B): １１ ~R １３ The structure excluding W is also simply called an ethylene unit. (In formula (B), W is a functional group having a function as an anion receptor, and R １１ ~R １３ are each independently a hydrogen atom or a monovalent substituent, or R １１ and R １３ One of them is R １２ and form a ring together, and the other is a hydrogen atom or a monovalent substituent. * indicates the position where the structural unit (B) is bonded to another structural unit. R １１ ~R １３may be hydrogen atoms, or all of may be hydrogen atoms.)

[0040] In formula (B), R １１ ~R １３ is a monovalent substituent, the monovalent substituent may be a monovalent organic group. The number of carbon atoms in the organic group may be, for example, 1 to 20, 1 to 15, 1 to 10, 1 to 5, or 1 to 3.

[0041] In formula (B), R １１ ~R １３ is a monovalent substituent, the monovalent substituent may have an electron-withdrawing group or may be the electron-withdrawing group itself. The electron-withdrawing group may be bonded to the monovalent organic group, or the monovalent organic group may be the electron-withdrawing group. Examples of the electron-withdrawing group include a halogen atom, a sulfonic acid group or a salt thereof, a sulfonic acid ester, a nitro group, and a nitrile group. The halogen atom may be a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom.

[0042] In formula (B), R １１ and R １３ One of them is R １２ When R forms a ring together with １１ or R １２ and R １３ form divalent substituents bonded to two carbon atoms of the ethylene unit of formula (B), respectively. These rings may be either carbocyclic or heterocyclic. The number of ring members of these rings may be, for example, 4 to 10, 5 to 8, 5, or 6. A substituent may be bonded to the carbon atom or heteroatom that is a ring member.

[0043] In formula (B), W preferably has a group represented by formula (B1) below. (In formula (B1), W Ｂ is an atom belonging to group 13 of the periodic table, and R １５ is a covalent bond or a divalent organic group, and R １６ and R １７ are each independently a hydrogen atom, an —OH group, a halogen atom, or a monovalent organic group, or are joined together to form a ring. １６ and R１７ may be the same group or different groups.)

[0044] In formula (B1), W Ｂ may be at least one of an aluminum atom and a boron atom, and may be a boron atom.

[0045] In formula (B1), R １５ When R is a divalent organic group, the number of carbon atoms in the divalent organic group may be, for example, 1 to 20, 1 to 15, 1 to 10, 1 to 5, or 1 to 3. １５ When is a divalent organic group, the organic group is a hydrocarbon group, a halogen-substituted hydrocarbon group, or a hydrocarbon group or a halogen-substituted hydrocarbon group bonded to W via an ether bond. Ｂ The halogen-substituted hydrocarbon group may be a hydrocarbon group in which some or all of the hydrogen atoms have been substituted with halogen atoms, and may be a partially fluorinated hydrocarbon group or a fully fluorinated hydrocarbon group. １５ may be a covalent bond.

[0046] In formula (B1), R １６ or R １７ is a halogen atom, R １６ or R １７ may be any of a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, and may also be a fluorine atom.

[0047] In formula (B1), R １６ or R １７ When R is a monovalent organic group, the number of carbon atoms in the monovalent organic group may be, for example, 1 to 20, 1 to 15, 1 to 10, 1 to 5, or 1 to 3. ６ or R ７ is a hydrocarbon group, a halogen-substituted hydrocarbon group, or a hydrocarbon group or a halogen-substituted hydrocarbon group connected to W via an ether bond Ｂ The halogen-substituted hydrocarbon group may be a hydrocarbon group in which some or all of the hydrogen atoms have been substituted with halogen atoms, and may be a partially fluorinated hydrocarbon group or a fully fluorinated hydrocarbon group.

[0048] The group represented by formula (B1) may be a group represented by formula (B1a) below or a group represented by formula (B1b) below. (In formula (B1a), R １５ is a covalent bond or a divalent organic group, and X １１ and X １２ are each independently an oxygen atom or a covalent bond. １１ is a covalent bond, R ２１ is a hydrogen atom, a halogen atom, or a monovalent organic group. １１ is an oxygen atom, R ２１ is a hydrogen atom or a monovalent organic group. １２ is a covalent bond, R ２２ is a hydrogen atom, a halogen atom, or a monovalent organic group. １２ is an oxygen atom, R ２２ is a hydrogen atom, a halogen atom, or a monovalent organic group. １１ and X １２ When each is an oxygen atom, they may be oxygen atoms that form an ether bond. (In formula (B1b), R １５ is a covalent bond or a divalent organic group, and X １３ and X １４ are each an oxygen atom or a covalent bond, and R ２３ is a divalent organic group.

[0049] In formula (B1a), R ２１ or R ２２ When R is a monovalent organic group, the monovalent organic group may be a monovalent hydrocarbon group or a monovalent halogen-substituted hydrocarbon group. The number of carbon atoms in the monovalent organic group may be, for example, 1 to 20, 1 to 15, 1 to 10, 1 to 5, or 1 to 3. The halogen-substituted hydrocarbon group may be a hydrocarbon group in which some or all of the hydrogen atoms have been substituted with halogen atoms, and may be a partially fluorinated hydrocarbon group or a fully fluorinated hydrocarbon group. ２１ or R ２２ When is a halogen atom, the halogen atom may be a fluorine atom.

[0050] In formula (B1a), R ２１ and R２２ are each independently —F, —CH ３ , -C ２ H ５ , -C ３ H ７ , -C ６ H ５ (phenyl group), —C ６ H ｎ F ５－ｎ (n is an integer of 0 to 4, and may be an integer of 0 to 3), -CF ３ , -CH ２ CF ３ , -CH ２ CF ３ CF ７ , -CH(CF ３ ) ２ , -C(CF ３ ) ２ -C ６ H ５ , -C(CF ３ ) ３ , -C ６ H ｎ (CF ３ ) ５－ｎ (n is an integer from 0 to 4, and may be 1 or 2.)

[0051] In formula (B1b), the divalent organic group may have, for example, 1 to 20, 1 to 15, 2 to 10, or 3 to 8 carbon atoms. The divalent organic group may be a hydrocarbon group or a halogen-substituted hydrocarbon group. The halogen-substituted hydrocarbon group may be a hydrocarbon group in which some or all of the hydrogen atoms have been substituted with halogen atoms, and may be a partially fluorinated hydrocarbon group or a fully fluorinated hydrocarbon group.

[0052] In formula (B1b), R ２３ is -C ２ H ４ -, -C ３ H ６ -, -C ４ H ８ -, -C ５ H １０ -, -C ６ H １２ -, -C ７ H １４ -, -C ８ H １６-, -C ９ H １８ -, -C １０ H ２０ -, etc., in which the hydrogen atoms are partially or entirely substituted with fluorine atoms. ２３ is -C(CH ３ ) ２ -C(CH ３ ) ２ - may be.

[0053] The polymer may contain a structural unit (C) that is neither the structural unit (A) nor the structural unit (B). The structural unit (C) may contain a structural unit (C) represented by the following formula (C): (In formula (C), R ２５ is a hydrogen atom or a monovalent substituent, and R ２６ ~R ２８ are each independently a hydrogen atom or a monovalent substituent, or R ２６ and R ２７ is a hydrogen atom or a monovalent substituent, and the other is R ２８ and form a ring. * indicates the bonding site of the structural unit (C) to other structural units.

[0054] In formula (C), R ２５ may be a monovalent organic group. The monovalent organic group is -Z １ -R ２９ R ２５ may have, for example, 1 to 40 carbon atoms, 1 to 20 carbon atoms, 2 to 15 carbon atoms, or 4 to 13 carbon atoms. １ is a divalent linking group, for example, a covalent bond, —O—, —S—, —C(═O)—, —C(═O)O—, —OC(═O)—, or —C(═O)NR ３８ -or-NR ３９ Z may be a group represented by C(=O)-. １ is a covalent bond, —O—, —S—, —C(═O)—, —C(═O)O—, or —OC(═O)—, R ２９ is a hydrogen atom or a monovalent organic group. １ -C(=O)NR ３８ -, then R ２９ , R３８ are each a hydrogen atom or a monovalent organic group, or R ２９ is R ３８ The divalent linking group Z １ But, -NR ３９ When C(=O)-, R ２９ , R ３９ are each a hydrogen atom or a monovalent organic group, or R ２９ is R ３９ It forms a ring together with R. ２９ , R ３８ and R ３９ The monovalent organic group as R may have, for example, 1 to 20 or 1 to 10 organic groups. ３８ When Z1 is a monovalent organic group, it may be a monovalent hydrocarbon group having 1 to 20 carbon atoms. When Z1 is a covalent bond or —C(═O)O—, R ２９ may be a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms. １ is a covalent bond and R ２９ When R is a hydrocarbon group, the hydrocarbon group may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group. ２９ may be a monovalent organic group other than a hydrocarbon group or a hydrocarbon group having a ring structure. １ When R is —O—, it may be a monovalent organic group other than the group represented by W—H when W is an alkyl ether. ２６ ~R ２８ When R is a monovalent organic group, the monovalent organic group is ２５ The same examples as those given above are included.

[0055] In a group having an aromatic ring (for example, the above-mentioned aromatic hydrocarbon group), a monovalent substituent may be bonded to the aromatic ring. Examples of the monovalent substituent include a monovalent organic group, and examples of the monovalent organic group include a substituted or unsubstituted hydrocarbon group, a group represented by the formula: -R ６１ - (W １ -R ６２ ) ｎ -W ２ R ６３ Examples include groups represented by the formula: -R ６１ - (W１ -R ６２ ) ｎ -W ２ R ６３ The group represented by the formula (I) may be bonded to the para position of the benzene ring. １ may be a divalent group such as -O-, -S-, -C(=O)- or -C(=O)O-, or may be -O-. ２ may be a divalent group such as —O—, —S—, —C(═O)— or —C(═O)O—, or may be —O—.

[0056] In the monovalent organic group, R ６１ is a covalent bond or a divalent organic group. The divalent organic group may be a divalent hydrocarbon group. The divalent hydrocarbon group may have 1 to 8 carbon atoms, 1 to 5 carbon atoms, or 1 to 3 carbon atoms. The hydrogen atoms bonded to the divalent hydrocarbon group may be substituted with a substituent such as a monovalent substituent (i.e., the divalent hydrocarbon group may be a substituted hydrocarbon group). Examples of the substituent include a halogen atom such as a fluorine atom. Specific examples of the divalent hydrocarbon group include a methylene group, an ethylene group, a 1,2-propylene group, a 1,3-propylene group, or a group in which some or all of the hydrogen atoms of these groups have been substituted with halogen atoms such as fluorine atoms, and may be a methylene group.

[0057] In the monovalent organic group, R ６２is a divalent organic group and may be a divalent hydrocarbon group. The divalent hydrocarbon group may have, for example, 1 to 8, 1 to 5, or 1 to 3 carbon atoms. The hydrogen atoms bonded to the divalent hydrocarbon group may be substituted with a substituent such as a monovalent substituent (i.e., the divalent hydrocarbon group may be a substituted hydrocarbon group). Examples of the substituent include a halogen atom such as a fluorine atom. The divalent hydrocarbon group may be a methylene group, an ethylene group, a 1,2-propylene group, a 1,3-propylene group, or a group in which some or all of the hydrogen atoms of these groups have been substituted with halogen atoms such as fluorine atoms, or may be an ethylene group. n may be, for example, 1 to 10, 1 to 5, or 1 to 3. n may be an integer or a rational number (for example, n is an average value across the structural units (B) in the polymer). When R is present in one structural unit, ６２ When there are multiple, they may be different or the same.

[0058] In the monovalent organic group, R ６３ may be a hydrogen atom or a monovalent hydrocarbon group. The number of carbon atoms in the monovalent hydrocarbon group may be, for example, 1 to 8, 1 to 5, or 1 to 3. The hydrogen atoms bonded to the monovalent hydrocarbon group may be substituted with a substituent such as a monovalent substituent (i.e., the monovalent hydrocarbon group may be a substituted hydrocarbon group). Examples of the substituent include a halogen atom such as a fluorine atom. The monovalent hydrocarbon group may be a methyl group, an ethyl group, an isopropyl group, an n-propyl group, or a group in which some or all of the hydrogen atoms in these groups have been substituted with halogen atoms such as fluorine atoms, or may be a methyl group.

[0059] When the polymer contains the structural unit (C), the structural unit (C) may contain at least one structural unit derived from a monomer represented by the following formula (C1). (wherein m is 0 to 4 and n is 0 to 10. R ２０ may be a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. The alkyl group may be a methyl group or an ethyl group, or may be a methyl group.

[0060] In formula (C1), m may be, for example, 1 to 3, 1 to 2, or 1. m may be an integer or an average value across all structural units derived from the monomer represented by formula (C1) contained in the polymer (in this case, m is a rational number). In formula (C1), n ​​may be, for example, 1 to 4, or 1 to 3. n may be an integer or an average value across all structural units derived from the monomer represented by formula (C1) contained in the polymer (in this case, n is a rational number).

[0061] When the polymer has the structural unit (C), R ２６ and R ２７ One of them is R ２８ When the structural unit (C) forms a ring together with the structural unit (C), the ring may have, for example, 4 to 10 members, 4 to 8 members, or 5 to 7 members. The structural unit (C) may be the following structural unit (C2). (In formula (C2), X represents an oxygen atom or —NR ２４ - is a tertiary amino group represented by R ２４ is a monovalent organic group, and R ２５ and R ２６ are each independently a hydrogen atom or a monovalent substituent.

[0062] In formula (C2), R ２４ The number of carbon atoms contained in R may be, for example, 1 to 20, 1 to 15, or 2 to 10. ２４ may be a hydrocarbon group or a hydrocarbon group substituted with fluorine, and may be an ethyl group, a 2,2,2-trifluoroethyl group, an n-dodecyl group, a cyclohexyl group, or a benzyl group.

[0063] The ratio of the structural unit (A) to all structural units contained in the polymer may be, for example, 0.2 to 0.95, 0.2 to 0.8, 0.3 to 0.7, or 0.4 to 0.6.

[0064] The ratio of the structural unit (C) to all structural units contained in the polymer may be, for example, 0.05 to 0.8, 0.2 to 0.8, 0.3 to 0.7, or 0.4 to 0.6. The ratio of the structural unit (C) to all structural units contained in the polymer may be, for example, 0.8 or less, 0.7 or less, 0.6 or less, or 0.3 or less.

[0065] The total ratio of the structural units (A) and (C) to all structural units contained in the polymer may be, for example, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, 0.9 or more, or 0.95 or more. The total ratio of the structural units (A) and (C) to all structural units contained in the polymer may be, for example, less than 1.0, or 0.97 or less. The total ratio of the structural units (A) and (C) to all structural units contained in the polymer may be, for example, 0.5 or more and less than 1.0, or 0.5 to 0.97.

[0066] The content of the structural unit (A) relative to the total mass of the polymer may be, for example, 25 to 95 mass %, 40 to 90 mass %, or 50 to 90 mass %.

[0067] The content of the structural unit (C) relative to the total mass of the polymer may be, for example, 5 to 75 mass%, 10 to 60 mass%, or 10 to 50 mass%, and the content of the structural unit (C) relative to the total mass of the polymer may be, for example, 75 mass% or less, 60 mass% or less, 50 mass% or less, or 25 mass% or less.

[0068] The total content of the structural unit (A) and the structural unit (C) relative to the total mass of the polymer may be, for example, 90% by mass or more, 95% by mass or more, or 98% by mass or more. The total content of the structural unit (A) and the structural unit (C) relative to the total mass of the polymer may be, for example, 100% by mass or less, less than 100% by mass, or 99% by mass or less. The total content of the structural unit (A) and the structural unit (C) relative to the total mass of the polymer may be, for example, 90 to 100% by mass.

[0069] When the polymer contains the structural unit (B), the molar ratio m of the structural unit (B) to all structural units contained in the polymer may be, for example, 0.2 to 0.8, 0.25 to 0.75, 0.3 to 0.7, 0.35 to 0.65, or 0.4 to 0.6. The content of the structural unit (B) relative to the total mass of the polymer may be, for example, greater than 10% by mass and 95% by mass or less, 15 to 95% by mass, 20 to 80% by mass, 25 to 60% by mass, or 30 to 45% by mass.

[0070] The number average molecular weight (Mn) of the polymer may be, for example, 5,000 to 400,000, 8,000 to 200,000, 10,000 to 150,000, or 10,000 to 100,000. The weight average molecular weight (Mw) of the polymer may be, for example, 5,000 to 600,000, 10,000 to 450,000, 20,000 to 200,000, or 20,000 to 100,000. The molecular weight distribution (Mw / Mn) of the polymer may be, for example, 1.0 to 5.0, 1.2 to 3.0, or 1.3 to 2.5. The number average molecular weight and weight average molecular weight of the polymer can be measured, for example, by gel permeation chromatography.

[0071] The polymer may be one that does not hydrolyze in air. The non-hydrolysis is determined based on the following criteria. First, the solution obtained by dissolving the polymer in a deuterated solvent is １ After that, the solution is stored under the atmosphere for 7 days (for example, at a temperature in the range of 25°C ± 10°C and at a humidity (which may be a relative humidity) of 65 ± 20%), and then the solution is again subjected to H-NMR measurement. １ A polymer is defined as "non-hydrolyzable" when the ratio of anionic functional groups protonated by hydrolysis to the anionic functional groups converted to an alkali metal by H-NMR measurement before storage is less than 10%. The ratio of protonated anionic functional groups may be, for example, 5% or less, or 1% or less.

[0072] The content of the polymer in the electrolyte composition may be, for example, 1 to 80 mass %, 3 to 70 mass %, 5 to 60 mass %, or 10 to 40 mass % relative to the total amount of the electrolyte composition.

[0073] The method for producing a polymer capable of preferentially conducting alkali metal ions is not particularly limited, but it can be produced, for example, by subjecting a corresponding monomer to a polymerization reaction such as radical addition polymerization.

[0074] <Ionic Compound> The ionic compound contains an anion having a donor number of 37 or less. Here, unless otherwise specified, the donor number of an anion in this specification is the donor number measured for a salt of the anion with 1-ethyl-3-methylimidazolium. The donor number in this specification is measured by the method of measuring SbCl in 1,1-dichloroethane as described in Schmeisser et al., Chemistry-A European Journal, 2012, 18, 10969-10982. ５ The donor number is based on a method for measuring the calorific value associated with the interaction with the alkali metal ion. The smaller the donor number, the weaker the interaction of the anion contained in the ionic compound with the cation. In other words, it is presumed that the cation of the ionic compound easily interacts with the anionic functional group of the polymer, and the anion of the ionic compound also weakly interacts with the alkali metal ion and does not strongly bind the alkali metal ion. By using such an ionic compound, the binding of the anionic functional group of the polymer to the alkali metal ion can be loosened, making it easier for the alkali metal ion to move in the electrolyte composition.

[0075] The donor number of the anion of the ionic compound may be, for example, 35 or less, 30 or less, 25 or less, or 20 or less. The donor number of the anion of the ionic compound may be, for example, −10 or more, −7 or more, −5 or more, 0 or more, 4 or more, 6 or more, 8 or more, 10 or more, or 11 or more. The donor number of the anion of the ionic compound may be, for example, −10 to 35, −5 to 35, or −5 to 20.

[0076] Anions with donor numbers of 37 or less include NO ３ － , ClO ４ － , P.F. ６－ , MBF ４ － , M ２ SO ４ － , [(C ｈ F ２ｈ＋１ ) SO ３ ] － (h is 0 to 3), [(C ｈ F ２ｈ＋１ ) SO ２ ] ２ N － (h is 0 to 3), {[(C ｈ F ２ｈ＋１ ) SO ２ ]N(C ｉ F ２ｉ＋１ ) SO ２ ] － (h and i are 0 to 3). The anion is CF ３ SO ３ － (OTf ion), [FSO ２ ] ２ N － (FSI ion), and [CF ３ SO ２ ] ２ N － (TFSI ion).

[0077] The ionic compound is not particularly limited, and examples thereof include alkali metal salts and compounds having organic cations. The electrolyte composition may contain at least one of an alkali metal salt and a compound having an organic cation. The formula weight of the ionic compound may be, for example, 800 or less, 500 or less, or 400 or less. The electrolyte composition may contain one or more ionic compounds. The electrolyte composition may also contain an ionic compound containing an anion having a donor number greater than 37. Examples of such ionic compounds include halides.

[0078] The weighted average of the donor numbers of the anions of the ionic compounds contained in the electrolyte composition may be, for example, 37 or less, 35 or less, 30 or less, 25 or less, or 20 or less. The weighted average of the donor numbers of the anions of the ionic compounds contained in the electrolyte composition may be, for example, 10 or more, 12 or more, or 15 or more. The weighted average of the donor numbers of the anions of the ionic compounds contained in the electrolyte composition may be, for example, 10 to 37, or 12 to 25. The weighted average donor numbers DN is calculated by the following formula (I): (In the formula, n is the total number of anions of the ionic compounds contained in the electrolyte composition and is 1 or more, D is the donor number of the i-th anion, and f is the mass fraction of the i-th anion.)

[0079] When the electrolyte composition contains a nonionic organic solvent, the donor number of the anion of the ionic compound can be selected in relation to the nonionic organic solvent. When the donor number of the ionic compound is smaller than the donor number of the nonionic organic solvent, the nonionic organic solvent is more likely to dissolve alkali metal ions (e.g., Li ＋ ) tends to be preferentially coordinated to the anion of the ionic compound, which makes it easier for the alkali metal ion to migrate. In addition, in a system in which a nonionic organic solvent and an ionic compound are used in combination, it is preferable that the anion of the ionic compound has a lower donor number, but it is particularly preferable to use one with a relatively large donor number, since this makes it easier to extract the alkali metal ion from the anionic functional group of the polymer that has the ability to preferentially conduct the alkali metal ion. On the other hand, when the donor number of the anion of the ionic compound is larger than the donor number of the nonionic organic solvent, the anion of the ionic compound tends to preferentially coordinate to the Li ＋ It tends to preferentially coordinate to cations such as

[0080] The ionic compound is preferably a compound in which B≦A, and more preferably B<A, where A is the Raman shift attributable to the anion constituting the ionic compound in the Raman spectrum obtained by Raman spectroscopy of the ionic compound and B is the Raman shift attributable to the anion constituting the ionic compound in the Raman spectrum obtained by Raman spectroscopy of the electrolyte composition. B<A means that the Raman shift of the ionic compound is shifted to the low wavenumber side (long wavelength side) in the electrolyte composition, and a so-called red-shift has occurred. The occurrence of a red-shift means that the anion portion of the ionic compound is an alkali metal ion (for example, Li ＋ ) is weak, so by using an ionic compound that generates the red shift as described above in the electrolyte composition, the movement of alkali metal ions can be made easier.

[0081] The difference between B and A (the value of A-B) is 0.0 or more, but may be, for example, 0.1 or more, 0.2 or more, or 0.3 or more. The value of A-B may also be, for example, 20.0 or less, 15.0 or less, 10.0 or less, 9.5 or less, 9.0 or less, 7.0 or less, 5.0 or less, 4.0 or less, 3.0 or less, 2.0 or less, 1.0 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, or 0.4 or less. The value of A-B may be, for example, 0.1 to 20.0.

[0082] The Raman shift in this specification refers to a value determined from a Raman spectrum obtained by performing Raman spectroscopy using a laser with a wavelength of 785 nm. For Raman spectroscopy, for example, a Raman spectrometer (device name: DXR3) manufactured by Thermo Fisher Scientific can be used. The Raman shift A and Raman shift B are peaks corresponding to deformation vibrations of an ionic compound. The Raman shift corresponds to the anion moiety in the ionic compound, and the anion is PF ６ － In the case of F-PF bending vibration, TFSI － or FSI－ In the case of , it corresponds to the bending vibration of SN, and OTf － In the case of C-S-O bending vibration, N(CN) ２ － In this case, it corresponds to the CNC bending vibration.

[0083] The compound having an organic cation may be an ionic liquid. The formal charge of the organic cation may be monovalent, but may also be divalent or higher. Examples of the compound having an organic cation include imidazolium salts, pyrrolidinium salts, piperidinium salts, pyridinium salts, quaternary ammonium salts, and quaternary phosphonium salts. The anion of the compound having an organic cation is not particularly limited, and may be, for example, Cl. － ,Br － , I － , ClO ４ － , P.F. ６ － , B.F. ４ － , C.F. ３ SO ３ － , (FSO ２ ) ２ N － , (CF ３ SO ２ ) ２ N － , (C ｒ F ２ｒ＋１ SO ２ ) ２ N － (r is an integer of 2 or more), HSO ３ － From the viewpoint of electrochemical stability, PF ６ － , B.F. ４ － , C.F. ３ SO ３ － , (FSO ２ ) ２ N － , (CF ３ SO ２ ) ２ N － Or (C ｍ F ２ｍ＋１ SO ２ )２ N － (FSO ２ ) ２ N － or (CF ３ SO ２ ) ２ N － (CF ３ SO ２ ) ２ N － The ionic liquid may be liquid at 25°C.

[0084] Examples of the pyrrolidinium cation contained in the pyrrolidinium salt include the following.

[0085] In the above formula, R ４１ and R ４２ are each independently a monovalent organic group, and the organic group preferably has 1 to 15 carbon atoms. The monovalent organic group may be an alkyl group having 1 to 15 carbon atoms, such as a butyl group, or a group represented by the formula: -A １ -O-(A ２ -O) ｋ -A ３ A group represented by １ is an alkylene group having 1 or 2 carbon atoms, A ２ is an alkylene group having 2 or 3 carbon atoms, A ３ is an alkyl group having 1 to 3 carbon atoms, and k is 0 to 3.

[0086] The above formula: -A １ -O-(A ２ -O) ｋ -A ３ The group represented by is preferably a group having 1 to 10 carbon atoms, and -CH ３ OCH ２ CH ２ OCH ３ group or —CH ２ CH ２ -O-CH ３ is more preferred. ４１ is an alkyl group having 1 to 3 carbon atoms and may be a methyl group. ４１ and R４２ may be the same or different. The hydrogen bonded to the carbon atom constituting the pyrrolidine ring may be substituted with a substituent.

[0087] Examples of the piperidinium cation contained in the piperidinium salt include the following.

[0088] In the above formula, R ４３ and R ４４ are each independently a monovalent organic group, and the organic group preferably has 1 to 15 carbon atoms. The monovalent organic group is preferably an alkyl group having 1 to 15 carbon atoms or a group of the formula: -A １ -O-(A ２ -O) ｋ -A ３ A group represented by １ is an alkylene group having 1 or 2 carbon atoms, A ２ is an alkylene group having 2 or 3 carbon atoms, A ３ is an alkyl group having 1 to 3 carbon atoms, and k is 0 to 3.

[0089] In the above formula, R ４４ More preferably, the alkyl group of formula: -A is an alkyl group having 2 to 6 carbon atoms, such as a butyl group. １ -O-(A ２ -O) ｋ -A ３ The group represented by is preferably a group having 1 to 10 carbon atoms, and -CH ３ OCH ２ CH ２ OCH ３ group or —CH ２ CH ２ -O-CH ３ is more preferred. ４３ is an alkyl group having 1 to 3 carbon atoms and may be a methyl group. ４３ and R ４４ may be the same or different. The hydrogen bonded to the carbon atom constituting the piperidine ring may be substituted with a substituent.

[0090] Examples of imidazolium cations contained in the imidazolium salt include the following.

[0091] In the above formula, R ４６ and R ４７ are each independently a monovalent organic group, and the organic group preferably has 1 to 15 carbon atoms. The monovalent organic group is preferably an alkyl group having 1 to 15 carbon atoms or a group of the formula: -A １ -O-(A ２ -O) ｋ -A ３ A group represented by １ is an alkylene group having 1 or 2 carbon atoms, A ２ is an alkylene group having 2 or 3 carbon atoms, A ３ is an alkyl group having 1 to 3 carbon atoms, and k is 0 to 3.

[0092] In the above formula, R ４７ The alkyl group of the formula: -A is preferably an alkyl group having 2 to 6 carbon atoms, such as a butyl group. １ -O-(A ２ -O) ｋ -A ３ The group represented by is preferably a group having 1 to 10 carbon atoms, and -CH ３ OCH ２ CH ２ OCH ３ group or —CH ２ CH ２ -O-CH ３ is more preferred. ４６ is an alkyl group having 1 to 3 carbon atoms and may be a methyl group. ４６ and R ４７ may be the same or different. The hydrogen bonded to the carbon atom constituting the imidazole ring may be substituted with a substituent.

[0093] Examples of the ammonium cation contained in the quaternary ammonium salt include the following.

[0094] In the above formula, R ５１ ~R５４ are each independently a monovalent organic group, and the organic group preferably has 1 to 15 carbon atoms. The monovalent organic group is preferably an alkyl group having 1 to 15 carbon atoms or a group of the formula: -A １ -O-(A ２ -O) ｋ -A ３ A group represented by １ is an alkylene group having 1 or 2 carbon atoms, A ２ is an alkylene group having 2 or 3 carbon atoms, A ３ is an alkyl group having 1 to 3 carbon atoms, and k is 0 to 3. ５１ ~R ５４ may all be the same, or may be two or more different groups. For example, R ５１ is an alkyl group having 1 to 10 carbon atoms, and R ５２ ~R ５４ is preferably an alkyl group having 1 to 3 carbon atoms, and R ５１ is an alkyl group having 3 to 8 carbon atoms, such as a butyl group, and R ５２ ~R ５４ is more preferably a methyl group or an ethyl group. １ -O-(A ２ -O) ｋ -A ３ The group represented by is preferably a group having 1 to 10 carbon atoms, and -CH ３ OCH ２ CH ２ OCH ３ group or —CH ２ CH ２ -O-CH ３ is more preferred.

[0095] Examples of the phosphonium cation contained in the quaternary phosphonium salt include the following.

[0096] In the above formula, R ５６ ~R ５９are each independently a monovalent organic group, and the organic group preferably has 1 to 15 carbon atoms. The monovalent organic group is preferably an alkyl group having 1 to 15 carbon atoms or a group of the formula: -A １ -O-(A ２ -O) ｋ -A ３ A group represented by １ is an alkylene group having 1 or 2 carbon atoms, A ２ is an alkylene group having 2 or 3 carbon atoms, A ３ is an alkyl group having 1 to 3 carbon atoms, and k is 0 to 3. ５６ ~R ５９ may all be the same, or may be two or more different groups. For example, R ５６ is an alkyl group having 1 to 10 carbon atoms, and R ５７ ~R ５９ is preferably an alkyl group having 1 to 3 carbon atoms, and R ５６ is an alkyl group having 3 to 8 carbon atoms, such as a pentyl group, and R ５７ ~R ５９ is more preferably a methyl group or an ethyl group.

[0097] The compound having an organic cation may contain one or more organic cations selected from the group consisting of a 1-ethyl-1-methylpyrrolidinium cation, a 1-n-propyl-1-methylpyrrolidinium cation, a 1-n-butyl-1-methylpyrrolidinium cation, a 1-n-propyl-1-methylpiperidinium cation, a 1-n-butyl-1-methylpiperidinium cation, a 1-ethyl-3-methylimidazolium cation, a butyltrimethylammonium cation, and a triethylpentylphosphonium cation. The compound having an organic cation may contain one or more anions selected from the group consisting of a hexafluorophosphate anion, a bis(fluorosulfonyl)imide anion, a bis(trifluoromethanesulfonyl)imide anion, and a trifluoromethanesulfonate anion.

[0098] Specific examples of the compound having an organic cation include 1-(2-methoxyethoxymethyl)-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-n-butyl-1-methylpyrrolidinium hexafluorophosphate 1-n-propyl-1-methylpyrrolidinium bis(fluorosulfonyl)imide, 1-n-propyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide, 1-n-butyl-1-methylpyrrolidinium bis(fluorosulfonyl)imide, 1-ethyl-1-methylpyrrolidinium bis(trifluoromethane ... phosphonium bis(trifluoromethylsulfonyl)imide, 1-n-propyl-1-methylpiperidinium bis(fluorosulfonyl)imide, 1-n-propyl-1-methylpiperidinium bis(trifluoromethanesulfonyl)imide, 1-n-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide, 1-n-butyl-1-methylpyrrolidinium trifluoromethanesulfonic acid, 1-n-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, triethyl-n-pentylphosphonium bis(trifluoromethanesulfonyl)imide, n-butyltrimethylammonium bis(trifluoromethanesulfonyl)imide, and the like.

[0099] The content of the compound having an organic cation in the electrolyte composition may be, for example, 5 to 400 parts by mole, 10 to 300 parts by mole, or 20 to 250 parts by mole per 100 parts by mole of the structural units of the polymer.

[0100] The alkali metal salts include MF, MCl, MBr, MI, and MNO, where M is an alkali metal. ３ , MClO ４ , MPF ６ , MBF ４ , M ２ SO ４ , M[(C ｈ F ２ｈ＋１ ) SO ３ ] (h is 0 to 3), M[(C ｈ F ２ｈ＋１ ) SO２ ] ２ N (h is 0 to 3), M{[(C ｈ F ２ｈ＋１ ) SO ２ ]N[(C ｉ F ２ｉ＋１ ) SO ２ ]} (h and i are 0 to 3), MBOB (BOB is bisoxalatoborate), etc. One or more alkali metal salts may be used. M is not particularly limited as long as it is an alkali metal, and may contain lithium, sodium, or potassium, or may contain lithium or sodium, or may contain potassium. The alkali metal element contained in the alkali metal salt may be the same alkali metal element as the alkali metal element contained in the structural unit (A).

[0101] The content of the alkali metal salt in the electrolyte composition may be, for example, 0.1 to 200 mol %, 2.5 to 150 mol %, 5 to 100 mol %, or 10 to 60 mol % in terms of alkali metal ions contained in the alkali metal salt relative to the total amount of the structural unit (A) contained in the polymer.

[0102] <Nonionic Organic Solvent> Examples of the nonionic organic solvent include aprotic solvents. The nonionic organic solvent may contain one or more organic solvents selected from the group consisting of carbonate-based solvents, ether-based solvents, fluorine-based solvents, nitrile-based solvents, lactone-based solvents, and phosphate-based solvents, and may contain a phosphate ester. The nonionic organic solvent may contain one or more solvents selected from the group consisting of carbonate-based solvents, ether-based solvents, fluorine-based solvents, nitrile-based solvents, phosphate ester-based solvents, and sulfone-based solvents, and may contain a carbonate-based solvent. In the electrolyte composition, the polymer may be swollen by the nonionic organic solvent.

[0103] Examples of carbonate solvents include chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate, and cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate. The organic solvent may be a mixed solvent containing two or more carbonate solvents, such as a mixed solvent containing one or more cyclic carbonate solvents and one or more chain carbonate solvents, or a mixed solvent containing two or more cyclic carbonate solvents.

[0104] Examples of the ether solvent include cyclic ethers such as tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, and 1,3-dioxolane; and chain ethers such as 1,2-diethoxyethane and ethoxymethoxyethane.

[0105] Examples of fluorine-based solvents include hydrofluorocarbons such as perfluorooctane; hydrofluoroethers such as methyl nonafluorobutyl ether and ethyl nonafluorobutyl ether; hydrofluoroolefins such as 1,3,3,3-tetrafluoropropene; and 2,2,2-trifluoro-N,N-dimethylacetamide.

[0106] Examples of the phosphate ester include trimethyl phosphate (TMP), triethyl phosphate (TEP), and tris(2,2,2-trifluoroethyl) phosphate (TFEP).

[0107] Examples of the nitrile solvent include acetonitrile, succinonitrile, etc. Examples of the lactone solvent include γ-butyrolactone, etc.

[0108] Other examples of nonionic organic solvents include sulfone solvents such as sulfolane and 3-methylsulfolane, solvents having a sulfonyl group such as dimethyl sulfoxide (DMSO), amide solvents such as dimethylformamide (DMF) and dimethylacetamide (DMA), organic solvents having a carbonyl group such as acetone (referring to carbonyl compounds other than amide compounds such as -C(=O)-, esters, ketones, and aldehydes), and nitrogen-containing aromatic compounds such as pyridine (compounds containing nitrogen as a ring member of the aromatic ring, which may be either monocyclic or fused ring systems). The nonionic organic solvent may be used alone or as a mixed solvent containing two or more organic solvents.

[0109] The nonionic organic solvent may have a dielectric constant of 21 or more. Use of a nonionic organic solvent with a high dielectric constant results in better affinity with ionic compounds. The dielectric constant of the nonionic organic solvent may be, for example, 25 or more, 30 or more, 35 or more, 40 or more, 45 or more, 50 or more, 55 or more, 60 or more, 65 or more, or 70 or more. The dielectric constant of the nonionic organic solvent may be, for example, 90 or less, 85 or less, or 80 or less. The dielectric constant of the nonionic organic solvent may be adjusted within the above-mentioned range and may be, for example, 25 to 90.

[0110] The dielectric constant in this specification means a value measured by the following method. First, a sample to be measured is sandwiched between two electrodes to form a capacitor, and the dielectric constant is determined from the capacitance value C measured for the capacitor. From the following equation, which stands upright for an ideal capacitor, the dielectric constant ε is calculated using the values ​​of C (capacitance), the electrode area S, and the electrode spacing d measured by a measuring instrument. ｒ Calculate C = ε ｒ ε ０ S / d When the nonionic organic solvent is a mixed solvent, a weighted average is calculated from the relative dielectric constant and mass fraction of each solvent, and the calculated value is regarded as the relative dielectric constant of the nonionic organic solvent.

[0111] The content of the nonionic organic solvent in the electrolyte composition may be, for example, 10 to 1000 parts by mass, 50 to 800 parts by mass, 100 to 600 parts by mass, 150 to 500 parts by mass, or 200 to 400 parts by mass relative to 100 parts by mass of the polymer contained in the electrolyte composition.

[0112] The transference number of the alkali metal ion of the electrolyte composition may be, for example, 0.5 or more, 0.6 or more, or 0.7 or more. The transference number of the alkali metal ion of the electrolyte composition may be, for example, 0.9 or less, or 0.85 or less. The transference number of the alkali metal ion of the electrolyte composition may be, for example, 0.5 to 0.9. The transference number may be measured at room temperature (25°C).

[0113] The electrolyte composition may further contain other resins such as fluorine-based resins (resins other than the above polymers, such as binder resins), fabrics such as nonwoven fabrics, porous materials, viscosity modifiers, anion receptors, etc. The electrolyte composition may contain, as the fluorine-based resin, a resin having a carbon chain as its main chain. The carbon chain may be formed by radical polymerization of an ethylenically unsaturated group. Examples of fluorine-based resins include poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and polyvinylidene fluoride (PVDF). The porous material may be a resin-based porous material. Specific examples include porous polyolefin membranes and porous ceramic membranes. The content of the other resin may be, for example, 1 to 200 parts by mass, 5 to 150 parts by mass, 10 to 100 parts by mass, or 10 to 80 parts by mass per 100 parts by mass of the polymer capable of preferentially conducting alkali metal ions.

[0114] The anion receptor is not particularly limited. The formula weight (molecular weight) of the anion receptor may be, for example, 1,000 or less, 800 or less, or 500 or less. The anion receptor may have Lewis acidity. In this case, the anion receptor can capture the anion by accepting the unshared electron pair of the anion and forming an acid-base complex. Examples of such compounds include compounds having an electron-deficient atom. Note that an electron-deficient atom refers to an atom that is covalently bonded to another atom but has fewer than eight electrons in its outermost shell. Examples of electron-deficient atoms include atoms belonging to Group 13 of the periodic table, and more specifically, may be at least one of an aluminum atom and a boron atom, or may be a boron atom.

[0115] Examples of anion receptors having a boron atom include boron compounds that function as Lewis acids, such as diborane and compounds represented by the following chemical formulas IA to IE.

[0116]

[0117] In Formulas IA and ID, R ３１ and R ３３ are each a halogen atom or a monovalent organic group. The halogen atom may be a fluorine atom or a chlorine atom, or may be a fluorine atom. The number of carbon atoms in the monovalent organic group may be, for example, 1 to 20, 1 to 15, 2 to 10, or 2 to 6. Here, the monovalent organic group is bonded to the boron atom (B) in formula IA or ID via a carbon atom in the monovalent organic group. The monovalent organic group may be a hydrocarbon group or a halogen-substituted hydrocarbon group, and the halogen-substituted hydrocarbon group may be a partially or fully fluorinated hydrocarbon group. In one molecule, multiple R ３１ and R ３３ may be different from each other or may all be the same.

[0118] In formulas IB and IE, R ３２ and R ３４are each a hydrogen atom or a monovalent organic group. The halogen atom may be a fluorine atom or a chlorine atom, or may be a fluorine atom. The number of carbon atoms in the monovalent organic group may be, for example, 1 to 20, 1 to 15, 2 to 10, or 2 to 6. Here, the monovalent organic group is bonded to the oxygen atom (O) in formula IB or IE via a carbon atom in the monovalent organic group. The monovalent organic group may be a hydrocarbon group or a halogen-substituted hydrocarbon group, and the halogen-substituted hydrocarbon group may be a partially or fully fluorinated hydrocarbon group. In one molecule, multiple R ３２ and R ３４ may be different from each other or may all be the same.

[0119] In formula IC, R ３５ is a divalent organic group, Z ２ is a covalent bond or an oxygen atom. The number of carbon atoms in the divalent organic group may be, for example, 1 to 15, 2 to 10, or 3 to 8. ３５ , two Zs ２ and the boron atom (B) form a ring, and the ring may have, for example, 4 to 8, 5, or 6 ring members. ２ When is an oxygen atom, the divalent organic group is connected to Z in formula IC by the carbon atom contained in the divalent organic group. ２ and Z ２ When Z is a covalent bond, the divalent organic group is bonded to the boron atom (B) in formula IC via a carbon atom contained in the divalent organic group. The divalent organic group may be a hydrocarbon group or a halogen-substituted hydrocarbon group, and the halogen-substituted hydrocarbon group may be a partially or fully fluorinated hydrocarbon group. In one molecule, multiple Z ２ may be different from each other or may all be the same.

[0120] In formula IC, R ３６ is a hydrogen atom or a monovalent organic group. The monovalent organic group may be a group that bonds to the boron atom (B) in formula IC via a carbon atom that the monovalent organic group has, but -OR ３７ R ３７is a hydrogen atom or a monovalent organic group. ３７ The monovalent organic group represented by the formula (I) is -OR ３７ It is bonded to the oxygen atom of R. ３６ or R ３７ The number of carbon atoms in the monovalent organic group may be, for example, 1 to 20, 1 to 15, 2 to 10, or 2 to 6. Here, the monovalent organic group is bonded to the boron atom (B) in Formula IA via a carbon atom contained in the monovalent organic group. The monovalent organic group may be a hydrocarbon group or a halogen-substituted hydrocarbon group, and the halogen-substituted hydrocarbon group may be a partially or fully fluorinated hydrocarbon group.

[0121] Specific examples of boron compounds include diborane, boron trifluoride, boric acid, boroxine, trimethylborane, triethylborane, tri-n-propylborane, triisopropylborane, triphenylborane, trimethylborate, triethylborate, triphenylborate, tri-n-propylborate, triisopropylborate, 2-methoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane, and 2-ethoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane. Examples thereof include organic boron compounds such as oran, 2,4,6-trimethylboroxine, 2,4,6-triethylboroxine, 2,4,6-trivinylboroxine, 2,4,6-trimethoxyboroxine, 2,4,6-trimethoxyboroxine, and triphenylboroxine; and halogen-substituted hydrocarbon groups such as tris(2,2,2-trifluoroethyl)borate, 2,4,6-tris(4-fluorophenyl)boroxine, and 2,4,6-tris(3,4,5-trifluorophenyl)boroxine.

[0122] The anion receptor having an aluminum atom includes an aluminum compound that functions as a Lewis acid, and has the formula AlX １ ３ (X １ is a halogen atom, which may be a fluorine atom), the formula: Al(OR ３５ ) ３ (R ３５is a hydrocarbon group, which may be an alkyl group.

[0123] The anion receptor may also be an azaether. An azaether is an ether compound in which —O— is replaced by —NR Ｅ - (where R Ｅ is a hydrogen atom or an organic group). The azaether may be either a linear azaether or a cyclic azaether. The azaether may have an electron-withdrawing group, for example, in the hydrocarbon moiety.

[0124] The content of the anion receptor in the electrolyte composition may be, for example, 10 to 200 parts by mass, 30 to 180 parts by mass, 50 to 150 parts by mass, or 80 to 130 parts by mass relative to 100 parts by mass of the polymer.

[0125] The method for producing the electrolyte composition is not particularly limited, but the electrolyte composition can be obtained by preparing a solution containing a polymer and an ionic compound, drying the solution, and then adding an organic solvent. In this case, the electrolyte composition may be used as a dried membrane, or may be impregnated into a porous material (e.g., a resin membrane) such as a separator and then dried.

[0126] The electrolyte composition of this embodiment can be used as a composition for forming an electrolyte for batteries, capacitors, etc. That is, the electrolyte of the battery of this embodiment may contain the electrolyte composition. Examples of the battery include batteries that charge and discharge by the movement of alkali metal ions, such as lithium ion batteries and sodium ion batteries. The battery may be a primary battery, a secondary battery, or a solid-state battery. The electrolyte composition of this embodiment may be used as an electrode material and may be contained in at least one of the positive electrode and the negative electrode.

[0127] The battery of this embodiment includes a positive electrode, a negative electrode, and an electrolyte disposed between the positive electrode and the negative electrode. The positive electrode may be a layer containing a positive electrode material formed on a current collector. The negative electrode may be a layer containing a negative electrode material formed on a current collector. The following description will be given taking a lithium-ion battery as an example.

[0128] The negative electrode of the lithium ion battery is not particularly limited and may contain a negative electrode active material and, if necessary, a conductive additive, a binder, etc. Examples of the negative electrode active material include simple elements such as Li, Si, P, Sn, Si—Mn, Si—Co, Si—Ni, In, and Au, alloys or composites containing these elements, carbon materials such as graphite, substances in which lithium ions are inserted between the layers of the carbon material, and oxides containing titanium.

[0129] The positive electrode of the lithium ion battery is not particularly limited, and may contain a positive electrode active material and, if necessary, a conductive additive, a binder, etc. The positive electrode active material is not particularly limited, and examples thereof include lithium composite metal oxides containing lithium and a transition metal element. The transition metal element may be at least one selected from the group consisting of V, Cr, Mn, Fe, Co, Ni, Cu, and Al, and may contain Ni. Examples of lithium composite metal oxides include LiCoO ２ , LiNiO ２ , LiMn ２ O ４ , LiNi ０．５ Mn １．５ O ４ , Li ２ MnO ３ , LiNi ｘ Mn ｙ Co １－ｘ－ｙ O ２ [0<x+y<1]), LiNi ｘ Co ｙ Al １－ｘ－ｙ O ２ [0<x+y<1]), LiCr ０．５ Mn ０．５ O ２ , LiFePO ４ , Li ２ FeP ２ O ７ , LiMnPO ４ , LiFeBO ３ , Li ３ V ２ (P.O. ４ ) ３ , Li ２ CuO ２ , Li ２ FeSiO４ , Li ２ MnSiO ４ When the positive electrode active material contains an alkali metal element other than Li, specific examples thereof include those in which Li in the above specific examples is replaced with another alkali metal.

[0130] The negative electrode (negative electrode material) and the positive electrode (positive electrode material) of this embodiment may further contain a solid electrolyte material, a binding resin (binder), a conductive assistant, and the like.

[0131] The battery may have a separator. The separator may be a porous material, such as a porous resin material. Specific examples of the separator include a porous polyolefin membrane and a porous ceramic membrane.

[0132] <Synthesis of Copolymer 1> 0.558 g of monomer X represented by the following formula, 0.149 g of styrene, and 11.7 mg of azobisisobutyronitrile were dissolved in 6.7 mL of dehydrated acetonitrile, and the mixture was reacted at 60°C for 24 hours under a nitrogen atmosphere while adding tetralin as an internal standard substance to check the monomer consumption rate. The polymerization solution was dialyzed in acetonitrile and vacuum dried at 120°C to obtain 0.640 g (yield 87%) of Copolymer 1. The monomer introduction ratio was monomer X:styrene = 52:48. The monomer introduction ratio was 0.640 g (yield 87%) of Copolymer 1. １ Calculated from H-NMR.

[0133] Number average molecular weight of copolymer 1 Mn = 9.4 × 10 ４ , weight average molecular weight Mw=4.2×10 ５ The molecular weight distribution Mw / Mn was 4.45. The number average molecular weight and weight average molecular weight were measured by gel permeation chromatography. The polymer was dissolved in a deuterated DMSO solvent. １ When H-NMH was measured, -SO ２ -NH-SO ２ No peaks due to protons from the - group were observed. After leaving this solution in the atmosphere at room temperature for 7 days, １ H-NMH was measured, but the peak derived from the proton was not confirmed. It was determined that Copolymer 1 does not undergo hydrolysis in air.

[0134]

[0135] The monomer X was synthesized by adding the following compound to an aqueous solution of lithium acetate (14.0 mmol, 0.92 g) in acetic anhydride (12.3 mL, manufactured by Tokyo Chemical Industry Co., Ltd.) and stirring at 70° C. for 3 hours.

[0136] <Preparation of Copolymer 2> A lithiated carboxyl group-containing copolymer was prepared by the following method.

[0137] Saccharin methacrylamide (SacM) (1.8848 g, 7.5 mmol), styrene (St) (0.86 mL, 7.5 mmol), tetralin (0.15 mL), and azobisisobutyronitrile (24.7 mg, 0.15 mmol) were dissolved in a mixed solvent of dioxane and acetonitrile (dioxane:acetonitrile=1:1 (volume ratio)) (12.1 mL), and the solution was stirred at 60° C. for 24 hours to obtain a solution of a copolymer of saccharin methacrylamide and styrene (raw material copolymer).

[0138] Next, a 25 mM phenothiazine solution in 1,4-dioxane (45.0 mL, 1.13 mmol) and 100 equivalents of water were added to the resulting polymerization solution, and the mixture was stirred overnight. As a result, the structural units derived from saccharin methacrylamide in the raw copolymer were hydrolyzed, and the amide bonds containing saccharin moieties were converted to -COOH groups (i.e., the structural units derived from saccharin methacrylamide were converted to methacrylic acid (MAA) units), yielding a -COOH group-containing copolymer (0.61 g).

[0139] The composition ratio of the structural units in the polymer was MAA:St = 48:52 (molar ratio). １ It was calculated by measuring the H-NMR spectrum.

[0140] Then, the -COOH group-containing copolymer (0.61 g, 3.21 mmol) was dissolved in dimethylformamide (12 mL) to obtain a solution. To this solution, 2.5 equivalents of LiOH (449.1 mg, 18.82 mmol) relative to the amount of SacM initially charged when producing the raw copolymer was added, and the mixture was stirred at room temperature (25°C) for 3 days. As a result, copolymer 2 (lithiated carboxyl group-containing copolymer) in which the -COOH groups of the -COOH group-containing copolymer were converted to -COOLi was obtained (0.43 g).

[0141] The solution obtained by dissolving the obtained polymer in deuterated DMSO solvent １ When H-NMH was measured, the peak due to the -COOH group, which was expected to be observed around 12 ppm, was not confirmed. １ H-NMH was measured, but no peaks derived from —COOH groups were confirmed, and it was determined that Copolymer 2 would not undergo hydrolysis in air.

[0142] (Examples 1 to 11, Comparative Examples 1 to 3) A polymer solution was prepared by dissolving 100 parts by mass of the copolymer obtained above, 50 parts by mass of PVdF-HFP, and an ionic compound in DMF according to the formulations shown in Tables 1 and 2. This solution was impregnated onto a PE separator, and then dried under reduced pressure at 80°C to obtain a composite membrane. To this composite membrane, a nonionic organic solvent (a mixed solvent of ethylene carbonate (EC) and propylene carbonate (PC) (1:1 volume ratio)) was added in an amount twice the weight of the composite membrane minus the weight of the PE separator, to obtain an electrolyte composition.

[0143] <Measurement of Maximum DC Current Density> An evaluation cell of a coin-type battery CR2032 was assembled in a glove box under a dry argon atmosphere. Specifically, each layer was laminated in the evaluation cell in the following order to prepare a test laminate (lithium / electrolyte composition / lithium).

[0144] The evaluation cell was subjected to alternating positive and negative currents of 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, and 2000 μA / cm ２ A constant current test was carried out in which current densities of 10 and 11 were applied in this order for 10 cycles, and the test was terminated when the voltage reached 2 V. The maximum current density that could be applied before reaching 2 V was defined as the maximum DC current density, and the voltage value at that time was determined. The results are shown in Tables 1 and 2.

[0145] <Measurement of Ionic Conductivity> An evaluation cell of a coin-type battery CR2032 was assembled in a glove box under a dry argon atmosphere. Specifically, each layer was laminated in the evaluation cell in the following order to prepare a test laminate (stainless steel plate / electrolyte composition / stainless steel plate).

[0146] Measurements were made using an impedance measuring device under the conditions of 25°C, a frequency range of 0.1 Hz to 1 MHz, and an applied voltage of 10 mV (vs. open circuit voltage). The ionic conductivity σ can be calculated using the following formula. In the formula, R represents the impedance value, A represents the area of ​​the sample, and t represents the thickness of the sample. The results are shown in Tables 1 and 2. σ (S cm －１ )=t(cm) / (R(Ω)×A(cm ２ ))

[0147] <Measurement of Activation Energy> Ion conductivity measurements using the above evaluation cell were also carried out under conditions of 30, 40, 50, 60, and 70°C, and the change in ionic conductivity with respect to temperature was measured. The activation energy was calculated from the slope of a graph of the common logarithm of ionic conductivity versus the reciprocal of temperature using the Arrhenius equation (logk = logA - Ea / RT, where k is the reaction rate constant, A is the frequency factor, Ea is the activation energy, R is the gas constant, and T is the absolute temperature). The results are shown in Tables 1 and 2.

[0148] <Measurement of Lithium Ion Transference Number> An evaluation cell of a coin-type lithium battery CR2032 was assembled in a glove box under a dry argon atmosphere. Specifically, each layer was laminated in the evaluation cell in the following order to prepare a test laminate (lithium / electrolyte composition / lithium).

[0149] The lithium ion transport number measurement method is introduced in Polymer, 28, 2324 (1987). That is, 10 mV is applied to the test laminate at room temperature (25° C.), and the initial current value (I ０ ) and steady-state current value (I ｓｓ ) was measured, and the interface resistance measured value R ０ and the measured interface resistance R after voltage application ＳＳ The lithium ion transport number (t Ｌｉ＋ ) was calculated. V in the formula is the applied voltage. The results are shown in Tables 1 and 2. Ｌｉ＋ =I ｓｓ (VI ０ R ０ ) / I ０ (VI ＳＳ R ＳＳ )

[0150] The abbreviations in the table are as follows: IC-1: Ionic compound (ionic compound having an organic cation) IC-2: Ionic compound (alkali metal salt) DN: Anion donor number for 1-ethyl-3-methylimidazolium salt P １４ PF ６ : 1-n-butyl-1-methylpyrrolidinium hexafluorophosphate (solid at room temperature) P １４ FSI: 1-n-butyl-1-methylpyrrolidinium bis(fluorosulfonyl)imide P １４ TFSI: 1-n-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide P １４ OTf: 1-n-butyl-1-methylpyrrolidinium trifluoromethanesulfonate P １４ N (CN) ２ : 1-n-butyl-1-methylpyrrolidinium dicyanamide EMITFSI: 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide N ４１１１ TFSI: n-butyltrimethylammonium bis(trifluoromethanesulfonyl)imide PP １４TFSI: 1-n-butyl-1-methylpiperidinium bis(trifluoromethanesulfonyl)imide Phos ２２２５ TFSI: Triethyl-n-pentylphosphonium bis(trifluoromethanesulfonyl)imide P １２ TFSI: 1-ethyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide

[0151] In addition, P １４ It is clear from the DN trends of salts other than the 1-ethyl-3-methylimidazolium salt in Table 3 that the donor number for the 1-ethyl-3-methylimidazolium salt of FSI is 37 or less. １３ refers to 1-n-propyl-1-methylpyrrolidinium cation, and PP １３ refers to the 1-n-propyl-1-methylpiperidinium cation (Source: Wang et al., Chem, 2019, 5, 364-375).

[0152] <Raman Spectroscopic Measurement of Ionic Compounds> Raman spectroscopy was performed on representative ionic compounds and electrolyte compositions used in the Examples and Comparative Examples. In the obtained Raman spectra, deformation vibrations of the anion moiety were observed, and the Raman shift values ​​were determined. In Example 1, P １４ PF ６ In Example 2, P １４ FSI was used, and in Example 3, P １４ TFSI was used, and in Comparative Example 1, P １２ N (CN) ２ Since the anion part is PF ６ － , FSI － , TFSI － and N (CN) ２ － The Raman shifts of the FPF, SNS, and CNC bending vibrations were observed. The results are shown in Table 4.

[0153]

[0154]

[0155]

[0156]

[0157] Examples 12 to 20 A polymer solution was prepared by dissolving 100 parts by mass of copolymer 2, 50 parts by mass of PVdF-HFP, and the ionic compounds shown in Table 5 in dimethylformamide. This solution was impregnated onto a polyethylene separator and then dried under reduced pressure at 80°C to obtain a composite membrane. To this composite membrane, an organic solvent (a mixed solvent of ethylene carbonate and propylene carbonate (volume ratio 1:1)) was added in an amount twice the mass of the composite membrane minus the weight of the PE separator, to obtain an electrolyte composition. Various measurements were performed on the obtained electrolyte composition as described above. Figures 1 and 2 show the results of measuring the maximum DC current density using the electrolyte compositions of Example 15 and Comparative Example 3, respectively. In Figures 1 and 2, the dark curves indicate the change in voltage (vertical axis on the left), and the light curves indicate the change in current (vertical axis on the right). As shown in the boxed area in Figure 2, the overvoltage became too large to continue the test, and no DC current flowed.

[0158]

[0159] Examples 21 to 23 Electrolyte compositions were obtained in the same manner as in Example 9, except that the organic solvent (a mixed solvent of ethylene carbonate (EC) and propylene carbonate (PC) (volume ratio 1:1)) was replaced with the solvents shown in Table 6. Using the obtained electrolyte compositions, evaluations were carried out in the same manner as in Example 1. The results are shown in Table 6. In Table 6, fluoroethylene carbonate is represented as FEC, trimethyl phosphate is represented as TMP, and triethyl phosphate is represented as TEP, and the solvent components in Table 6 indicate volume ratios.

[0160]

Claims

1. An electrolyte composition comprising: a polymer capable of preferentially conducting alkali metal ions; and an ionic compound, the ionic compound comprising an anion having a donor number of 37 or less as measured on a 1-ethyl-3-methylimidazolium salt.

2. The electrolyte composition according to claim 1, wherein the transport number of the alkali metal ion is 0.5 or more.

3. The electrolyte composition of claim 1 or 2, wherein the polymer capable of preferentially conducting alkali metal ions comprises lithium ions or sodium ions.

4. The electrolyte composition according to claim 1 or 2, wherein the ionic compound is a compound in which, when A is a Raman shift originating from an anion constituting the ionic compound in a Raman spectrum obtained by Raman spectroscopy of the ionic compound, and B is a Raman shift originating from an anion constituting the ionic compound in a Raman spectrum obtained by Raman spectroscopy of the electrolyte composition, B≦A.

5. The electrolyte composition according to claim 1 or 2, further comprising a non-ionic organic solvent.

6. The electrolyte composition according to claim 5, wherein the nonionic organic solvent comprises one or more organic solvents selected from the group consisting of carbonate-based solvents, ether-based solvents, fluorine-based solvents, nitrile-based solvents, lactone-based solvents, phosphate-based solvents, and sulfone-based solvents.

7. The electrolyte composition according to claim 5, wherein the nonionic organic solvent has a relative dielectric constant of 21 or more.

8. The electrolyte composition according to claim 1 or 2, wherein the functional group having an anion includes one or more groups selected from the group consisting of an alkali metal substituted sulfonylimide group, an alkali metal substituted sulfonic acid group, and an alkali metal substituted carboxylic acid group.

9. The electrolyte composition of claim 1 or 2, wherein the polymer capable of preferentially conducting alkali metal ions does not hydrolyze in air.

10. A battery comprising the electrolyte composition according to claim 1 or 2.

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